20 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



in the main terminal and lateral roots. These roots gave the 

 Peroxidase reaction in the cortex; roots not possessing the 

 internal fungus never did so. 



Thus it appears that wherever the internal fungus is present 

 in a rootlet, the cortical cells in which the fungus is present 

 show Oxidase or Peroxidase. In normal roots without 

 mycorhiza there is no Peroxidase or Oxidase in the cortex. In 

 all cases these can be demonstrated in the central cylinder. 



Endotrophic mycorhiza-bearing plants, therefore, have a 

 large supply of oxidising materials at their disposal as 

 compared with plants with normal roots. 



II. — EcTOTROPHic Mycorhiza. 



In the case of Ectotrophic mycorhiza and Peroxidase or 

 Oxidase production the plants tested were Abies grandis, 

 Tsuga albertiana, Picea sitchensis, Pi?ius contorta, and Pinus 

 sylvestris. 



In the first species, Abies graiidis, the contrasts in root-type 

 were obtained from plants in peat and in nursery soil, the 

 former bearing mycorhiza, the latter not bearing mycorhiza. 

 In Abies grandis, the fungus forms an envelope round the whole 

 rootlet, and penetrates inwards between the cells of the cortex 

 until within a cell layer or so of the endoderm. When 

 sectioned fresh and placed with the utmost speed in a 

 guaiacum alcoholic solution, the blue colour appeared instantly 

 on the addition of hydrogen peroxide, forming a well-defined 

 blue ring round the section, conforming to the band of envelop- 

 ing fungus ; between the cells of the cortex, conforming to the 

 passage of the mycelium inwards ; and in the wood elements of 

 the central cylinder. No such result could be obtained in 

 rootlets without mycorhiza, the Peroxidase reaction only being 

 obtained in the central cylinder. 



Similar results were obtained with Tsuga albertiana. In 

 one case here, in roots taken from a laboratory plant in peat 

 where the fungus was only present between the cells of the 

 cortex, the deep blue colour only appeared between the cells 

 of the cortex and in the central cylinder. In roots where the 

 fungus v^as absent no blue colour appeared, except in the 

 central cylinder. 



In Sitka spruce. Pinus contorta^ and Scots pine, in every 



